Stability of multi-walled carbon nanotube+laponite hybrid particles in aqueous suspensions

Abstract

Abstract Aggregation of multi-walled carbon nanotube (NT) + laponite hybrid particles in aqueous suspensions under continuous stirring at different values of mass ratio of laponite and NTs, X = m L / m NT , was investigated using Photometric Dispersion Analyser. It has been found that NTs + laponite suspension at X = 1 is the most stable in respect to variation of pH and electrolytes concentration. Addition of electrolytes (KCl, CaCl 2 and AlCl 3 ) destabilized the suspension with formation of large quickly sedimenting flocs. Also the strength of flocs and the reversibility of aggregation of NT + laponite nanoparticles as a function of the shear rate have been determined. From time dependencies of the degree of aggregation in hybrid NTs + laponite suspensions, the critical coagulation concentrations (CCC) for KCl (CCC 1 = 5 × 10 −3 M), CaCl 2 (CCC 2 = 10 −3 M) and AlCl 3 (CCC 3 = 10 −5 M) for the NTs + laponite complex suspension were estimated. The ratio of CCC 1 /CCC 2 ≈ 5 is very close to the CCC z 2.5 = 5.66 criterion. It is an evidence of aggregation of NT + laponite hybrid particles in the secondary minimum.